Message from "System Administrator" saying message "Undeliverable: RE: <subject text>"

[#1]

Has anybody any idea what sort of thing would cause the message below? I have no problem sending or receiving messages generally and I can receive from this customer without any problem but every time I hit reply and try and answer their message something throws the biggest strop going and totally refuses!

Your message did not reach some or all of the intended recipients.

      Subject:    RE: <subject text>

      Sent: 25/02/2022 17:49

The following recipient(s) cannot be reached:

      '<contact>@<customer>.eu' on 25/02/2022 17:49

            552 Nei2n2tfalLBXNei3nd46V message rejected due to spam or virus. If you believe this is in error please login to your portal or contact your ISP support team.

      '<me>@<sending domain hosted by plusnet>.co.uk' on 25/02/2022 17:49

            552 Nei2n2tfalLBXNei3nd46V message rejected due to spam or virus. If you believe this is in error please login to your portal or contact your ISP support team.

I have checked their message for web links and removed any - doesn't fix it. I have removed recipients so all that is left is actually the copy back to me - doesn't fix it. I have started a totally new message and copied the text of the email into that, specifying plain text message - doesn't fix it! I have previously removed increasing amounts of the original message to me and finally managed to get it to send so it isn't the recipients email address that is the issue.

I am tearing my hair out trying to work out what it is in their message that is causing the problem.

HELP!!!

[#2]

This is the problem
"552 Nei2n2tfalLBXNei3nd46V message rejected due to spam or virus. If you believe this is in error please login to your portal or contact your ISP support team."

The PlusNet email servers are likely to be on some kind of SPAM Blacklist and the recipient servers are blocking emails from the PlusNet servers. Its nothing to do with the message its the servers which are sending it. This happens a lot across the internet, often with Microsoft hosted accounts - PlusNet will need to contact the receiving org and ask for its servers to be removed from the blacklist.

[#3]

I wish it were that easy 😢

The message isn't being accepted by Plusnet's own email servers for some unknown reason. If I look at the headers from the bounce message from "System Administrator" there are none/they are empty and there is no email address for the System Administrator.

[#4]

I think I have finally worked out what Plusnet's server was complaining about - maybe !

- If my outgoing email had the <contact>@<company>.eu address in it the message failed to send

- if I replaced the email address with the contacts name and made no other change to the message it sent

The only hitch is that I tried sending myself a message with the problem email address in it and it successfully sent. 😖😢 Aghhhh!

[#5]

Are you suggesting that if the body of the email contains only "<contact>@<company>.eu" Plusnet's outbound server refuses to accept the email for transmission?

If that is the case then the reason for the transmission being blocked is that the above email address has been associated with questionable activity resulting in a lot of people reporting email from that address as being spam.

[#6]

I sort of thought that but I am sending the email to the person that the server didn't seem to like if their email address is in the message body and it eventually sent when I took that out. I tried to confirm by sending myself a message with the same email address in the body and it sent without a problem (but not if I sent myself the original message which was failing). 😭

It is the weirdest thing and seems to be restricted to this one company (a customer!). It is perfectly possible the company is on some blacklist but given its size (global engineering firm) I would have hoped their IT department was competent enough to stop that happening.

I could ignore the problem if there was a consistent fix when it happened but there doesn't seem to be any consistency in what I need to change/remove to make the message send (or there hasn't been so far). If it is always removing any of the customers own email addresses from the body of the message so be it but I can't really ask them to send me lots of messages to reply to and then see what works.😕

[#7]

@Gandalf 

Can some one please seek full details from the user via PM to pass to support (JW)?

This could be a false positive in Cloud Mark ... or might be (as suggested) a CM Community based filter due to poor reputation.

Thanks

[#8]

Hi @itbookworm

I'm sorry to see your e-mails are being rejected. Could you private message me your account username, the unredacted bounceback, and a full copy of the headers of the e-mail you've tried to send, which was rejected?

The headers of the e-mail would need to be within 10 days for our NetOps team to take a look at the logs, and as it can take them a few days for them to get around to it as they're busy folk, I'd recommend sending a fresh e-mail at the time of messaging me then grabbing the headers from that. 

[#9]

That time-frame may be 7 days. Seems to be a little bit of confusion within NetOps, but I've asked for clarification.

Either way though, providing as fresh examples as possible will mean there's plenty of time for an investigation.